1. Field of the Invention
The present invention relates to shredders for destroying articles, such as documents, compact discs, etc.
2. Description of Related Art
Shredders are well known devices for destroying articles, such as paper, documents, compact discs (“CDs”), expired credit cards, etc. Typically, users purchase shredders to destroy sensitive information bearing articles, such as credit card statements with account information, documents containing company trade secrets, etc.
A common type of shredder has a shredder mechanism contained within a housing that is removably mounted atop a container. The shredder mechanism typically has a series of cutter elements that shred articles fed therein and discharge the shredded articles downwardly into the container. The shredder typically has a stated capacity, such as the number of sheets of paper (typically of 20 lb. weight) that may be shredded at one time; however, the feed throat of a typical shredder can receive more sheets of paper than the stated capacity. This is typically done to make feeding easier. A common frustration of users of shredders is to feed too many papers into the feed throat, only to have the shredder jam after it has started to shred the papers. To free the shredder of the papers, the user typically reverses the direction of rotation of the cutter elements via a switch until the papers become free.
The assignee of the present application, Fellowes, Inc., has developed thickness sensing technologies for shredders. By sensing thickness of the articles being fed, the shredder can be stopped (or not started) before a jam occurs. See U.S. Patent Application Publication Nos. 2006-0219827 A1, 2006-0054725 A1, 2007-0007373 A1 and 2007-0221767 A1, and U.S. patent application Ser. No. 11/867,260, each of which is incorporated by reference herein in their entirety.
Sheet capacity, shredding speed, and energy efficiency are three important parameters of a shredder. Prior art shredders have attempted to address the issue of energy efficiency or energy savings by using a closed-loop feedback based motor control circuits. For example, see U.S. Patent Publication Nos. 2007-0164135 A1 and U.S. Pat. No. 6,997,408, each of which is incorporated by reference herein in their entirety.